Open Universe Research Articles

Dissecting the regions around IceCube high-energy neutrinos: growing evidence for the blazar connection

ABSTRACT The association of two IceCube detections, the IceCube-170922A event and a neutrino flare, with the blazar TXS 0506+056, has paved the way for the multimessenger quest for cosmic accelerators. IceCube has observed many other neutrinos but their origin remains unknown. To better understand the reason for the apparent lack of neutrino counterparts, we have extended the comprehensive dissection of the sky area performed for the IceCube-170922A event to all 70 public IceCube high-energy neutrinos that are well reconstructed and off the Galactic plane. Using the multifrequency data available through the Open Universe platform, we have identified numerous candidate counterparts of IceCube events. We report here the classification of all the γ-ray blazars found and the results of subsequent statistical tests. In addition, we have checked the 4LAC, 3FHL, and 3HSP catalogues for potential counterparts. Following the dissection of all areas associated with IceCube neutrinos, we evaluate the data using a likelihood-ratio test and find a $3.23\, \sigma$ (post-trial) excess of HBLs and IBLs with a best fit of 15 ± 3.6 signal sources. This result, together with previous findings, consistently points to a growing evidence for a connection between IceCube neutrinos and blazars, the most energetic particle accelerators known in the Universe.

Finite action principle revisited

We extend the cosmological predictions from assuming the total action of the universe is finite. When initial and final singularities in curvature invariants are avoided, it leads to singularities in the gravitational action of the universe. The following properties are required of a universe with finite action: Compact spatial sections (ie a closed universe) giving a finite total lifetime for the universe. Compactification of flat and open universes is excluded. The universe can contain perfect fluids with -1<p/\r{ho}<2 on approach to singularities. The universe cannot display a bounce' or indefinite cyclic behaviour to the past or the future. We find new consequences of imposing finite action: the universe cannot be dominated by massless scalar fields, the kinetic energy of scalar fields, or a p=\r{ho} perfect fluid on approach to the initial or final singularity The ekpyrotic scenario with an effective fluid obeying p/\r{ho}>2 in a closed, flat or open universe is excluded. Any bouncing model with indefinite past or future evolution is ruled out. Einstein static and steady-state universes are ruled out along with past or future eternal inflating universes. Anisotropies cannot dominate the dynamics at singularities. This excludes density inhomogeneity spectra versus mass, of the form {\delta}\r{ho}/\r{ho}proportional to M^{-q}, with q>2/3.Higher-order lagrangian theories of gravity are constrained. The Gauss-Bonnet combination causes an action singularity even though it does not contribute terms to the field equations. Scalar-tensor theories dominated by the scalar field on approach to singularities have action singularities. Dark energy cannot be a cosmological constant. The dark energy must evolve in a closed universe that collapses to a future singularity that cannot be dominated by the kinetic energy of the scalar field.

Inhomogeneous perturbations and stability analysis of the Einstein static universe in $f(R,T)$ gravity

The purpose of this paper is to analyze the existence of static stable Einstein universe using inhomogeneous linear perturbations in the context of $f(R,T)$ gravity ($R$ and $T$ denote the scalar curvature and trace of the stress-energy tensor, respectively). The static and perturbed field equations are constructed for perfect fluid parameterized by linear equation of state parameter. We obtain solutions manifesting the Einstein static state by considering peculiar $f(R,T)$ forms for vanishing and non-vanishing conservation of the stress-energy tensor. It is observed that stable static Einstein regions exist for both closed as well as open FLRW universe models for an appropriate choice of parameters. We conclude that this theory is efficient for presenting such cosmological solutions leading to emergent universe scenario.

The United Nations Open Universe Initiative

AbstractIn this contribution I will briefly introduce the concept and objectives of the Open Universe Initiative, as well as describe the first steps of its implementation by Brazil, in conjunction with the United Nations Office for Outer Space Affairs (UNOOSA), aiming to encourage new interested parties to join the Initiative.

Open Universe for Blazars: a new generation of astronomical products based on 14 years ofSwift-XRT data

Aims.Open Universe for Blazars is a set of high-transparency multi-frequency data products for blazar science, and the tools designed to generate them. Blazars are drawing growing interest following the consolidation of their position as the most abundant type of source in the extragalactic very high-energyγ-ray sky, and because of their status as prime candidate sources in the nascent field of multi-messenger astrophysics. As such, blazar astrophysics is becoming increasingly data driven, depending on the integration and combined analysis of large quantities of data from the entire span of observational astrophysics techniques. The project was therefore chosen as one of the pilot activities within the United Nations Open Universe Initiative, whose objective is to stimulate a large increase in the accessibility and ease of utilisation of space science data for the worldwide benefit of scientific research, education, capacity building, and citizen science.Methods.Our aim is to deliver innovative data science tools for multi-messenger astrophysics. In this work we report on a data analysis pipeline calledSwift-DeepSky based on theSwiftXRTDAS software and the XIMAGE package, encapsulated into a Docker container.Swift-DeepSky downloads and reads low-level data, generates higher level products, detects X-ray sources, and estimates several intensity and spectral parameters for each detection, thus facilitating the generation of complete and up-to-date science-ready catalogues from an entire space-mission data set.Results.As a first application of our innovative approach, we present the results of a detailed X-ray image analysis based onSwift-DeepSky that was run on allSwift-XRT observations including a known blazar, carried out during the first 14 years of operations of theNeil Gehrels SwiftObservatory. Short exposures executed within one week of each other have been added to increase sensitivity, which ranges between ∼1 × 10−12and ∼1 × 10−14erg cm−2s−1(0.3–10.0 keV). After cleaning for problematic fields, the resulting database includes over 27 000 images integrated in different X-ray bands, and a catalogue, called 1OUSXB, that provides intensity and spectral information for 33 396 X-ray sources, 8896 of which are single or multiple detections of 2308 distinct blazars. All the results can be accessed online in a variety of ways, from the Open Universe portal through Virtual Observatory services, via the VOU-Blazar tool and the SSDC SED builder. One of the most innovative aspects of this work is that the results can be easily reproduced and extended by anyone using the Docker version of theSwift-DeepSky pipeline, which runs on Linux, Mac, and Windows machines, and does not require any specific experience in X-ray data analysis.

From Questioning to Answering: The Paranoid Dialectics of P. K. Dick

With reference to the work of American science fiction writer Philip K. Dick and the two Blade Runner films based on his writings, this commentary briefly explores the notion of totality (both closed and open) as it relates to psychoanalysis and politics. Where the original Blade Runner film pointed to a bleak but open universe, the newer film presents one sutured closed, with the promise of making each subject whole. With an eye to Žižek’s understanding of ideology, Lacan’s take on the “paranoid structure of knowledge,” and P. K. Dick’s understanding of totality, it becomes clear that an important aspect of ideology is the move from asking questions to providing answers. Where the former opens up possibilities that have no answers, the latter reduces politics to empirical choice.

Non-minimally coupled nonlinear spinor field in Bianchi type-I cosmology

Within the scope of Bianchi type-$I$ cosmological model we have studied the role of spinor field in the evolution of the Universe. In doing so we have considered the case with non-minimal coupling. It was found that the non-diagonal components of the energy-momentum tensor of the spinor field, hence the restrictions on the space-time geometry remain the same as in case of minimal coupling. Since in this case the diagonal components of the energy-momentum tensor differ, the evolution of the corresponding universe also differs. For example, while a linear spinor field with non-minimal coupling or nonlinear spinor field with minimal coupling give rise to open universe, a nonlinear spinor field with non-minimal coupling with the same parameters can generate close universe that at the beginning expands, and after attaining some maximum value begin to contract and finally ends in a Big Crunch.

The Spatially Closed Universe

The general world model for homogeneous and isotropic universe has been roposed. For this purpose, we introduce a global and fiducial system of reference (world reference frame) constructed on a 5-dimensional space-time that is embedding the universe, and define the line element as the separation between two neighboring events that are distinct in space and time, as viewed in the world reference frame. The effect of cosmic expansion on the measurement of physical distance has been correctly included in the new metric, which differs from the Friedmann-Robertson-Walker metric where the spatial separation is measured for events on the hypersurface at a constant time while the temporal separation is measured for events at different time epochs. The Einstein's field equations with the new metric imply that closed, flat, and open universes are filled with positive, zero, and negative energy, respectively. We have demonstrated that the flat universe is empty and stationary, equivalent to the Minkowski space-time, and that the universe with positive energy density is always spatially closed and finite. In the closed universe, the proper time of a comoving observer does not elapse uniformly as judged in the world reference frame, in which both cosmic expansion and time-varying light speeds cannot exceed the limiting speed of the special relativity. We have also reconstructed cosmic evolution histories of the closed world models that are consistent with recent astronomical observations, and derived useful formulas such as energy-momentum relation of particles, redshift, total energy in the universe, cosmic distance and time scales, and so forth. It has also been shown that the inflation with positive acceleration at the earliest epoch is improbable.

$$\hbox {Venn}_{i_{o1}}$$: A Diagram System for Universe Without Boundary

A new diagram system $$\hbox {Venn}_{i_{o1}}$$ where properties are fundamental and an object exists only w.r.t a property is presented. This work modifies both in syntax and semantics the system $$\hbox {Venn}_{i_{o}}$$ proposed by Choudhury and Chakraborty to picturise and address issues connected with open universe. Semantics for the current system is given. Soundness and completeness w.r.t the semantics are established.

The periodic universe with varying deceleration parameter of the second degree

In the present paper, we propose a new law for the deceleration parameter of the second degree of the time. Our law tells us about the behavior of the universe. According to our law, the spatially closed, flat and open universes are allowed, and the universe passes through with a big-rip and then retreats as it was in the moment of the big bang. The law we suggest covers the law of Berman, where the deceleration parameter is constant, also covers the law of the deceleration parameter of the first degree of time obtained by Akarsu and Tekin.

Effect of the spatial curvature of the Universe on the form of the gravitational potential

Within the cosmic screening approach, we obtain the exact formulas for the velocity-independent gravitational potentials produced by matter in the form of discrete sources distributed in the open and closed Universes. These formulas demonstrate that spatial curvature of the Universe considerably affect the form of the potentials and forces. While in the open Universe the gravitational force undergoes exponential suppression at cosmological distances, in the closed Universe the force induced by an individual mass is equal to zero at the antipodal point with respect to this mass. The derived formulas are applicable for investigations of the motion of astrophysical objects (e.g., galaxies) in the open and closed Universes, and for simulations of the large scale structure formation.

New inflation in the landscape and typicality of the observed cosmic perturbation

We investigate if the observed small and nearly scale-invariant primordial cosmic perturbation, i.e. the perturbation amplitude $P_\zeta\sim10^{-9}$ and the spectral index $n_s \simeq 0.965$, is typical in the landscape of vacua after imposing anthropic selections on them. We consider the situation where the universe begins from a metastable vacuum driving a precedent inflation, a curvature-dominated open universe is created by tunneling, and the curvature energy is inflated away by new inflation. We argue that the initial inflaton field value is homogeneous but typically non-zero because of the quantum fluctuation of long wavelength modes created during the precedent inflation, and only the universe which accidentally has a small inflaton field value is anthropically selected. We show that this bias, together with certain distributions of inflation model parameters that are physically well-motivated, makes the observed small and nearly scale-invariant spectrum typical.

Big Bounce and Closed Universe from Spin and Torsion

Abstract We analyze the dynamics of a homogeneous and isotropic universe in the Einstein–Cartan theory of gravity. The coupling between the spin and torsion prevents gravitational singularities and replaces the Big Bang with a nonsingular big bounce, at which the universe transitions from contraction to expansion. We show that a closed universe exists only when the product of the scale factor and temperature is higher than a particular threshold, contrary to a flat universe and an open universe, which are not restricted. During inflation, this product must increase to another threshold, so that the universe can reach dark-energy acceleration.

Indeterminismo y democracia en K.R. Popper

Popper's political thought, particularly his idea of democracy, is usually thought akin to that of the liberal tradition. We don't challenge this position here, but claim the Popperian idea of democracy gains full meaning when some key ideas of Popper's own cosmology and epistemology are taken into account. Our contention is that Popper's political perspective is indeed rooted in his criticism to physical determinism and his studies on indeterminism. Notions such as "open universe" and "open society", when taken together, provide a key to a liberal interpretation of cosmology and a physical interpretation of democracy.

Open Universe Models as Analogs of Multidimensional Electric Capacitors

A new approach to obtaining open Universes models as exact solutions of gravitational equations is considered. The proposed method is based on an analogy between electrostatics of conductors and open cosmological models which have a conformally-flat 4-metric in the Fock form. These cosmological models are solutions of the Einstein equations with the energy-momentum tensor of a Pascal perfect fluid. As a result, it is shown that the capacity of the multidimensional "ball" electric capacitor in multidimensional Euclidean auxiliary space is connected with harmonic functions by which the potentials of multidimensional capacitors are described. In turn, the conformal factor of the metric describing an open universe model in the Fock representation is a power function of this potential for each dimensionality of the Euclidean space. In particular, for 3D auxiliary Euclidean space in 4D space-time, there is the Friedman solution for an open universe filled with incoherent dust (with flat metric at spatial infinity). Further for 4D Euclidean space, we have an analogue of the open cosmological model with the equation of state of an ultra-relativistic gas. Other cases are listed in a table. A table of the matter states which generalizes this approach to multidimensional space-times is also constructed. Thus, the possibility of replacing the modelling problem in cosmology with the equivalent electrostatic problem for finding the capacity of capacitors is shown under specified boundary conditions. Exceptions from the general approach are also presented in the article.

Prática comunicativa no portal do MEC: Um estudo do plano da expressão

O Ministério da Educação (MEC) é responsável por legislar, criar, gerenciar e cobrar leis que se aplicam à educação do nosso país, exercendo, dessa forma, o papel de destinador social. A fim de aderir às novas formas de interação que as práticas comunicativas contemporâneas exigem, o MEC passou a se comunicar com a sociedade não apenas por meio dos textos impressos (documentos, manuais etc.), mas também por meio de práticas comunicativas digitais espalhadas pelos diversos espaços da Internet. Considerando que essas práticas digitais ocorrem em um universo hipersemiotizado, multimodal, híbrido e aberto, perguntamo-nos, neste trabalho, como se configurariam as práticas comunicativas do Ministério da Educação nesse novo ambiente, especificamente em seu Portal na Internet. Com o objetivo de responder a essas questões, propusemo-nos analisar o modo como o MEC organiza a prática da visita em seu site e como harmoniza o encadeamento das cenas enunciativas partindo de um estudo do suporte planar através das categorias cromáticas, topológicas e eidéticas desse espaço, compreendendo, dessa forma, as categorias do plano de expressão e, por conseguinte, as do plano de conteúdo, com base no modelo de análise da semiótica greimasiana, especialmente através dos níveis de pertinência de análise de Fontanille (2008) e do modelo de análise do texto sincrético proposto por Teixeira (2009, 2013). O estudo da prática comunicativa do MEC em seu portal nos permitiu comprovar as estratégias persuasivas decorrentes do sincretismo empregado na mídia digital e observar a experiência interpretativa do interlocutor que navega pelo espaço.

Inhomogeneous perturbations and stability in f ( G , T ) $f(\mathcal{G},T)$ gravity

In this paper, we study stability of the Einstein static universe against inhomogeneous scalar perturbations parameterized by equation of state parameter in \(f(\mathcal{G},T)\) gravity (\(\mathcal{G}\) and \(T\) represent the Gauss-Bonnet invariant and trace of energy-momentum tensor, respectively). We formulate static as well as perturbed field equations in the presence of perfect fluid and analyze the stability regions. This is accomplished for particular \(f(\mathcal{G},T)\) models corresponding to zero as well as non-zero covariant divergence of the energy-momentum tensor. It is found that stable Einstein universe exists both for spatially closed as well as open universe models for suitable choice of parameters.

The United Nations Open Universe Initiative for Open Data in Space Science

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Dissecting the region around IceCube-170922A: the blazar TXS 0506+056 as the first cosmic neutrino source

We present the dissection in space, time, and energy of the region around the IceCube-170922A neutrino alert. This study is motivated by: (1) the first association between a neutrino alert and a blazar in a flaring state, TXS 0506+056; (2) the evidence of a neutrino flaring activity during 2014 - 2015 from the same direction; (3) the lack of an accompanying simultaneous $\gamma$-ray enhancement from the same counterpart; (4) the contrasting flaring activity of a neighbouring bright $\gamma$-ray source, the blazar PKS 0502+049, during 2014 - 2015. Our study makes use of multi-wavelength archival data accessed through Open Universe tools and includes a new analysis of Fermi-LAT data. We find that PKS 0502+049 contaminates the $\gamma$-ray emission region at low energies but TXS 0506+056 dominates the sky above a few GeV. TXS 0506+056, which is a very strong (top percent) radio and $\gamma$-ray source, is in a high $\gamma$-ray state during the neutrino alert but in a low though hard $\gamma$-ray state in coincidence with the neutrino flare. Both states can be reconciled with the energy associated with the neutrino emission and, in particular during the low/hard state, there is evidence that TXS 0506+056 has undergone a hadronic flare with very important implications for blazar modelling. All multi-messenger diagnostics reported here support a single coherent picture in which TXS 0506+056, a very high energy $\gamma$-ray blazar, is the only counterpart of all the neutrino emissions in the region and therefore the most plausible first non-stellar neutrino and, hence, cosmic ray source.

Interacting and noninteracting dark energy models in f(R) gravity

In this paper, we study cosmic evolution and current expansion via generalized ghost pilgrim dark energy (PDE) model for FRW universe in [Formula: see text] gravity. For this purpose, we consider both interacting and non-interacting forms of dark energy (DE) model and reconstruct [Formula: see text] model using red-shift parameter. In order to analyze the effects of the DE model, we formulate some standard cosmological parameters such as Hubble, effective equation of state (EoS) and statefinder parameters as well as [Formula: see text]–[Formula: see text] plane. We also investigate the stability criteria for both interacting and noninteracting models through the squared speed of sound. It is concluded that the best-fit results are found for the positive curvature parameter in the presence of the noninteracting model. For the interacting model, the cosmic evolution is well explained by closed and open universe models while the flat geometry effectively describes the current cosmos.